ATLANTA -- On Saturday, Nationals outfielder Steven Souza Jr. said his left shoulder was feeling better after crashing into the right-field wall the day before. As it turned out, Souza's shoulder is much worse than expected. He was placed on the 15-day disabled list because of a shoulder contusion.

According to manager Matt Williams, Souza couldn't swing a bat on Saturday, and he was sent to Washington on Sunday to get the shoulder checked out by the team doctor. Souza pinch-ran for Jayson Werth in the top of the 11th inning Saturday.

"We put him through some tests yesterday, and he couldn't swing. It was very painful to swing the bat," Williams said. "So we decided to go ahead and send him back to get an MRI, make sure that the shoulder is OK. He hit that wall pretty hard."

Souza's injury occurred in the bottom of the second inning against the Braves on Friday. Freddie Freeman hit a 2-1 pitch from right-hander Stephen Strasburg to right field. Souza chased after the ball and collided with the wall at full speed as the ball went over the fence for a two-run homer.

Souza was on the ground for at least one minute, while Williams, athletic trainer Lee Kuntz and several teammates came to his aide.